Semiconductor devices such as an LSI (Large Scale Integrated circuit) are manufactured by performing a plurality of processes, such as etching, CVD (Chemical Vapor Deposition), or sputtering, on a substrate to be processed which is a semiconductor substrate (wafer). These processes are performed by generating plasma in a processing container and supplying a reaction gas into the processing container, in a plasma processing apparatus.
When plasma processing is performed, a pressure in the processing container is sometimes decreased to a point where the processing container is in a high vacuum state, that is, an extremely low pressure state. Here, when the pressure in the processing container is decreased, a vacuum apparatus for performing depressurization by using an APC (Auto Pressure Controller) valve having a variable conductance function for controlling a pressure to a predetermined pressure which is disclosed in Japanese Laid-Open Patent Publication No. 2006-295099 (Patent Document 1) may be used.    [Patent Document 1] Japanese Laid-Open Patent Publication No. 2006-295099